HLR / HSS / UDM Architect

Key Responsibilities

• Manage and operate HLR, HSS, UDR, and UDM nodes across 2G, 3G, 4G, and 5G core domains, ensuring high availability and data integrity for subscriber profiles.
• Design and maintain subscriber provisioning workflows, including IMSI/MSISDN management, service profiles, and roaming configurations.
• Implement and verify MAP, Diameter (S6a, S6d, Cx, Sh, Zh), and HTTP/2-based (N8, Nudm) interfaces connecting subscriber data nodes to MSC, MME, AMF, SGSN, and other core elements.
• Use and build dashboards to monitor subscriber node KPIs, quickly surface abnormal conditions, and identify patterns before they become outages.
• Own incident management for the subscriber data domain: follow communications procedures for internal escalation and external vendor coordination, ensuring SLAs are met.
• Perform maintenance, security audits, patching, and emergency response for HLR/HSS/UDM/UDR platforms.
• Undertake fault handling and corrective actions at node, service, and infrastructure level, including protocol trace analysis (Wireshark/tcpdump) on Diameter, MAP, and HTTP/2 signaling.
• Led and contribute to project activities: E2E introduction of new subscriber management nodes, capacity expansions, software upgrades, and feature activations.
• Support MVNO onboarding by configuring subscriber data repositories, IMSI ranges, and roaming agreements in HLR/HSS/UDM/UDR systems.
• Participate in 7x24 on-call rotation, including shift monitoring, babysitting activities during maintenance windows, and emergency response.
• Provide, implement, and verify improvements to processes and work instructions; drive automation of repetitive provisioning and audit tasks.
• Collaborate with IMS, RAN, and transport teams to resolve cross-domain subscriber authentication and registration issues.

Key Qualifications

• At least 10 years of experience in core network engineering with a focus on subscriber data management in mobile networks.
• BSc degree in Telecommunications, Computer Science, or equivalent; post-graduate studies are a plus.
• 10+ years of core telecommunications network experience, with a minimum of 5 years hands-on with HLR, HSS, UDR, or UDM platforms.
• Deep operational knowledge of HLR platforms (e.g., Ericsson HLR, Nokia FlexiISN, Huawei HLR9820) and their MAP/TCAP/SCCP signaling stacks.
• Hands-on experience with HSS platforms and Diameter-based interfaces: S6a, S6d, Cx, Sh, Zh — including Diameter routing agent (DRA) configuration and troubleshooting.
• Practical experience with 5G UDM and UDR, including cloud-native deployments (containerized/Kubernetes-based NFs) and HTTP/2 SBI interfaces (N8, Nudm_SubscriberDataManagement, Nudr_DataRepository).
• Solid understanding of subscriber profile structures: EPS subscription data, 5GS subscription, IMS subscription (Cx/Sh), CAMEL service data, and operator-determined barring.
• Experience with IMSI/MSISDN range management, number portability (NP/MNP) integration, and SIM/eSIM provisioning workflows.
• Strong knowledge of SS7 stack: MAP (Mobile Application Part), TCAP, SCCP, MTP — including MAP operations for location update, authentication, subscriber info retrieval, and SMS routing.
• Practical experience with Diameter protocol expertise: peer configuration, routing, AVP manipulation, error handling, and Diameter watchdog/transport management.
• Familiarity with 3GPP standards governing subscriber data: TS 23.008, TS 29.272 (S6a), TS 29.328/29.329 (Sh), TS 29.503/29.504 (UDM/UDR SBI), TS 23.502 (5G procedures).
• Understanding of roaming architecture, IR.21 data, IREG testing, and GSMA interconnect requirements relevant to subscriber data exchange.
• Working knowledge of 2G (HLR/AuC/VLR), 3G (HSS/HLR), 4G (MME/HSS/EPC), and 5G SA (AMF/SMF/UDM/UDR/AUSF/UDSF) core architectures and their subscriber data flows.
• Comfortable with Linux/Unix-based systems — able to navigate shells, interpret logs, manage processes, and perform basic system administration on telecom NF hosts.
• Experience with high-availability configurations for subscriber databases: active/standby, geo-redundancy, and database replication/synchronization.

Technical — Protocols & Standards

• Strong knowledge of SS7 stack: MAP (Mobile Application Part), TCAP, SCCP, MTP — including MAP operations for location update, authentication, subscriber info retrieval, and SMS routing.
• Practical experience with Diameter protocol expertise: peer configuration, routing, AVP manipulation, error handling, and Diameter watchdog/transport management.
• Familiarity with 3GPP standards governing subscriber data: TS 23.008, TS 29.272 (S6a), TS 29.328/29.329 (Sh), TS 29.503/29.504 (UDM/UDR SBI), TS 23.502 (5G procedures).
• Understanding of roaming architecture, IR.21 data, IREG testing, and GSMA interconnect requirements relevant to subscriber data exchange.

Technical — Network & Systems

• Working knowledge of 2G (HLR/AuC/VLR), 3G (HSS/HLR), 4G (MME/HSS/EPC), and 5G SA (AMF/SMF/UDM/UDR/AUSF/UDSF) core architectures and their subscriber data flows.
• Comfortable with Linux/Unix-based systems — able to navigate shells, interpret logs, manage processes, and perform basic system administration on telecom NF hosts.
• Experience with high-availability configurations for subscriber databases: active/standby, geo-redundancy, and database replication/synchronization.

Soft Skills & Ways Of Working

• Strong written and verbal communication skills in English — able to produce clear incident reports, change request documentation, and runbooks.
• Able to work under pressure during high-severity incidents while maintaining methodical troubleshooting discipline.
• Effective at interacting with external vendors, MVNO partners, and cross-functional internal teams.
• Adaptable and comfortable driving change in a fast-moving MVNO environment.
• Ready to work on morning/afternoon shifts and participate in on-call rotation.

Nice to Have

• 2+ years of scripting experience (Python, Bash) for automation of provisioning, audit, and reconciliation tasks on HLR/HSS/UDM/UDR systems.
• Experience with AUSF, UDSF, or PCF in 5G SA environments.
• Familiarity with cloud-native telecom platforms (OpenShift, Kubernetes) and Helm-based NF lifecycle management.
• Exposure to OSS/BSS integration for subscriber data, including provisioning APIs and mediation layer design.
• Knowledge of eSIM (GSMA SGP.02 / SGP.22) and its interaction with subscriber data repositories.
• Experience with MVNO/MVNE operating models and multi-tenant subscriber data isolation.